Isoroku Yamamoto (4 April1884 – 18 April1943) was a Fleet Admiral and Commander-in-Chief of the Imperial Japanese Navy (IJN) during World War II. He was a graduate of the Imperial Japanese Naval Academy and an alumnus of the U.S. Naval War College and Harvard University. He died during an inspection tour of forward positions in the Solomon Islands when his transport aircraft was ambushed by American P-38 Lightning fighter planes. His death was a major blow to Japanese military morale during World War II.

Should hostilities once break out between Japan and the United States, it is not enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians, among whom armchair arguments about war are being glibly bandied about in the name of state politics, have confidence as to the final outcome and are prepared to make the necessary sacrifices.

As quoted in At Dawn We Slept (1981) by Gordon W. Prange, p. 11; this quote was stated in a letter to Ryoichi Sasakawa prior to the attack on Pearl Harbor. Minus the last sentence, it was taken out of context and interpreted in the U.S. as a boast that Japan would conquer the entire contiguous United States. The omitted sentence showed Yamamoto's counsel of caution towards a war that would cost Japan dearly.

A military man can scarcely pride himself on having "smitten a sleeping enemy"; it is more a matter of shame, simply, for the one smitten. I would rather you made your appraisal after seeing what the enemy does, since it is certain that, angered and outraged, he will soon launch a determined counterattack.

Reply made to Ogata Taketora, the Editor in Chief of Asahi Shimbun (9 January 1942) as quoted in The Reluctant Admiral (1979) by Hiroyuki Agawa

In the first six to twelve months of a war with the United States and Great Britain I will run wild and win victory upon victory. But then, if the war continues after that, I have no expectation of success.

Statement to Japanese cabinet minister Shigeharu Matsumoto and Japanese prime minister Fumimaro Konoe, as quoted in Eagle Against the Sun: The American War With Japan (1985) by Ronald Spector. This remark would later prove prophetic; precisely six months after the attack on Pearl Harbor, the Japanese navy would suffer a major defeat at the Battle of Midway, from which it never recovered.

The fiercest serpent may be overcome by a swarm of ants.

Statement in opposition of the planned construction of the Yamato class battleships, as quoted in Scraps of paper: the disarmament treaties between the world wars (1989) by Harlow A. Hyde. In this statement, Yamamoto implies that even the most powerful battleships can be sunk by a huge swarm of carrier planes. This remark also proved prophetic as both Yamato and Musashi would be sunk by overwhelming air attacks.